Many cartons, particularly those associated with take-out foods, are formed of relatively thin material wherein the lid is of a substantial unsupported expanse and tends to sag and contact the contents of the box to the detriment of the contents.
A well known example of such a carton, and the problems caused by a tendency of the lid to centrally sag, is the conventional pizza box. Similar problems will also be noted in folded paperboard containers for cakes, pies and the like, particularly when the containers are stacked.
In order to avoid or minimize this problem, various forms of internal supports have been devised, including plastic spacers which are relatively expensive for a throwaway item. Another solution provides for a tear-away section of the carton which is subsequently formed into a spacer for insertion within the carton, a rather complex and time consuming procedure which could in fact damage the carton if not properly done. An additional proposal involves the use of tabs folded from the carton itself. This, particularly if folded from the top or bottom of the carton, could further weaken the carton at the critical area, as well as provide undesirable openings into the interior of the carton. Other solutions involve the use of various forms of preform supports which are not only bulky, causing shipping and storage expenses, but also must, at some point, be inserted in the individual cartons or boxes.